I eat a similar diet. I'm 6'0 and around 145. You are obviously undereating total calories if you are at 122. I recently completed a 7 day water fast and even on day 7 was much heavier than you.

Are you weight training? That is the best way to gain weight.

I suggest you download and start using the cron-o-meter to track your calories (as well as other stuff) and make sure you are eating enough. I typically eat well over 2000 cals/day, sometimes 3000 or more depending on my activity level and hunger.